[v3] app/testpmd: fix IP checksum calculation
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Commit Message
Strict-aliasing rules are violated by cast to uint16_t* in flowgen.c and
the calculated IP checksum is wrong. Use attribute __may_alias__ to fix
the problem.
Signed-off-by: George Prekas <prekageo@amazon.com>
---
v3:
* Instead of a compiler flag, use a compiler attribute.
v2:
* Instead of a compiler barrier, use a compiler flag.
---
app/test-pmd/flowgen.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
Comments
On 1/7/2021 8:42 PM, George Prekas wrote:
> Strict-aliasing rules are violated by cast to uint16_t* in flowgen.c and
> the calculated IP checksum is wrong. Use attribute __may_alias__ to fix
> the problem.
>
> Signed-off-by: George Prekas <prekageo@amazon.com>
Fixes: e9e23a617eb8 ("app/testpmd: add flowgen forwarding engine")
Cc: stable@dpdk.org
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>
Applied to dpdk-next-net/main, thanks.
@@ -53,8 +53,11 @@ static struct rte_ether_addr cfg_ether_dst =
#define IP_DEFTTL 64 /* from RFC 1340. */
+/* Use this type to inform GCC that ip_sum violates aliasing rules. */
+typedef unaligned_uint16_t alias_int16_t __attribute__((__may_alias__));
+
static inline uint16_t
-ip_sum(const unaligned_uint16_t *hdr, int hdr_len)
+ip_sum(const alias_int16_t *hdr, int hdr_len)
{
uint32_t sum = 0;
@@ -150,7 +153,7 @@ pkt_burst_flow_gen(struct fwd_stream *fs)
next_flow);
ip_hdr->total_length = RTE_CPU_TO_BE_16(pkt_size -
sizeof(*eth_hdr));
- ip_hdr->hdr_checksum = ip_sum((unaligned_uint16_t *)ip_hdr,
+ ip_hdr->hdr_checksum = ip_sum((const alias_int16_t *)ip_hdr,
sizeof(*ip_hdr));
/* Initialize UDP header. */